Fluid actuated track sanding mechanism



J. l. MORGAN Dec. 19, 1967 FLUID ACTUATED TRACK SANDING MECHANISM 4 Sheets-Sheet 1 Filed May 6, 1963 INVENTOR. Jam-2s. L. MORGAN ATTORNEY 1967 .1. l. MORGAN 3,359,024

FLUID ACTUATED TRACK SANDINGMECHANISM Filed May 6, 1963 4 Sheets-Sheet 2 t; 'W H8 6 I 6 us 24 I26 108 INVENTOR F 6 5 JA ES 1. MORGAN BY w. v

ATTORNEY Dec. 19, 1967 Filed y 6, 1963 J. I. MORGAN 3,359,024

FLUID ACTUATED TRACK SANDING MECHANISM 4 Sheets-Sheet :5

IINVENTOR. J Ame-.5 1. Moae m ATTORNEY J. l. MORGAN Dec. 19, 1967 4 Sheets-Sheet 4 Filed May 6 1963 m m 07 0fm 2 0. mm m n w m w 0. m M An 3 Jill J w v@ Y: 2 Y1 I"! 0m. w @2 W E FE!" If. g N2 United States Patent 3,359,024 FLUID ACTUATED TRACK SANDING MECHANHSM James I. Morgan, Hales Corners, Wis., assignor to The Prime Manufacturing Company, Milwaukee, Wis., a

corporation of Wisconsin Filed May 6, 1963, Ser. No. 278,072 18 Claims. (Cl. 291-3) This invention relates to improvements in sanding systems for railway locomotives.

Prior to this invention the conventional locomotive sanding arrangement for applying sand to the rails at the locomotive drive wheels includes a sand trap for delivering sand to the rails and a pneumatically actuated control valve for controlling the how of operating air to the trap. For a detailed description of the construction and operation of a pneumatically actuated control valve of the type referred to above and the sanding system in which it is used, reference is made to US. Patent No. 2,589,794, issued Mar. 18, 1952.

One of the principal problems inherent in prior sanding systems using pneumatically actuated control valves was the time required to apply sand to the rails once the operation of the system was initiated. This problem is particularly acute in multiple locomotive unit driving arrangements which predominate in current railroad practice. Further problems result from the relative complexity of prior equipment which is reflected in higher initial and maintenance costs and reduced reliability.

The primary objects of this invention are to overcome the above stated problems of prior systems. Specifically, it is one object of this invention to provide a system which will respond almost instantaneously to a call for sand at the rails. Another object is to provide a system the components of which are of relatively simple construction resulting in a reduced cost and greater reliability.

Another important objective of the preferred embodiment of'this invention is the provision of an added sanding function not heretofore present in conventional systems. Such added function is provided by a means for sensing a clogged condition in the sand delivery conduit and for automatically producing an increased flow of air to the sand trap to relieve such condition. When the restriction is removed the system automatically returns to normal sanding operation.

The objects of this invention are attained in the preferred embodiment by a sanding mechanism comprising a sand trap connected to a source of air under pressure by an air delivery conduit. A solenoid operated on-oif valve means and a sensor-charger valve means are mounted in the delivery conduit with the sensor-charger valve positioned upstream from the solenoid valve. The sensorcharger valve means has a inlet and an outlet and is adapted to admit an initial large volume air blast to the trap upon opening of the solenoid valve and to thereafter permit a reduced volume of air to how to the sand trap as long as said on-off valve means remains open. The sensor-charger valves is further adapted to admit an increased volume of air to the trap in response to an increase of pressure at the outlet of the sensor-charger valve means as might result from the occurrence of an air flow obstruction in the sand delivery line.

Broadly stated, the sensor-charger valve is comprised of a poppet valve means and a pressure sensitive piston means which cooperate to permit a large volume air blast to the trap upon initial opening of the solenoid valve and to further sense the presence of an air obstruction in the sand delivery line and to then cause such poppet valve to open and thereby admit a large volume air blast to the trap to remove the obstruction.

In the preferred embodiment both the on-otf solenoid valve and the sensor-charger valve are mounted in a bracket member which in turn is removably mounted on the sand trap for ease of maintenance and replacement of the component parts.

In another more simplified embodiment, the sensorcharger valve is replaced by an air restriction means which is connected upstream of the solenoid valve by a line which serves as an accumulator chamber to admit a high volume blast of air to the sand trap upon initial opening of the solenoid valve followed by a reduced volume of air for normal sanding metered by the air restriction means. This arrangement will not sense the occurrence of an obstruction during normal sanding and provide a high volume blast to clear such obstruction as will the sensorcharger valve in the preferred embodiment briefly described above.

Other objects and advantages will be pointed out in, or be apparent from the specification and claims, as will obvious modifications of the two embodiments shown in the drawings, in which:

FIG. 1 is a side elevation view of one embodiment of the sanding mechanism of this invention;

FIG. 2 is a sectional view of the sensor-charger valve taken along line 2-2 of FIG. 1;

FIG. 3 is a partial sectional view of the solenoid operated on-otf valve showing how it is connected to the nozzle of the sand trap;

FIG. 4 is a side elevation view of a modified form of the sanding mechanism;

FIG. 5 is a sectional view taken along line 5-5 of FIG. 4;

FIG. 6 is a sectional view FIG. 5;

FIG. 7 is a top plan view of the preferred embodiment of the sanding mechanism of this invention;

FIG. 8 is an end elevation view of the sanding mechanism shown in FIG. 7;

'FIG. 9 is a sectional view taken along line 9-9 of FIG. 8;

FIG. 10 is a sectional view taken along line Ill-10 of FIG. 7;

FIG. 11 is a sectional view taken along line 11-11 of FIG. 10;

FIG. 12 is a sectional view taken along line 12-12 of FIG. 10; and

FIG. 13 is an enlarged end view of the poppet valve member of the sensor-charger valve shown in FIG. 9.

Referring to the embodiment shown in FIGS. 1, 2 and 3, the sanding system includes a sand trap 10 having a sand delivery line 12 leading to the rail adjacent a locomotive drive wheel (not shown) and a sand supply conduit 14 connected to a sand box 16 for feeding sand by gravity to the trap. Trap 10 may be 'of any conventional design and has a nozzle 18 (FIG. 3) through which air under pressure is introduced to carry sand from feed inlet 20 out through discharge outlet 22 to delivery line 12. A sand on-off valve 24 and a sand pipe check valve 26 are provided in sand supply pipe 14 as shown. The specific function of check valve 26 will be explained in detail hereinafter.

As previously stated, air to trap 10 in prior sanding arrangements was controlled by a pneumatic control valve adapted to introduce an initial short high volume blast of air to nozzle 18 to clean out the nozzle, trap and delivery line followed by a steady reduced flow for applying sand to the rails for normal sanding. One shortcoming of such prior arrangements was the inherent time delay between the instant the actuating air signal to the control valve was initiated and the time sand was finally delivered to the rails. Such time delay increases with the taken along line 6-6 of 3 length of the air delivery lines as is the case when the sanding systems of several locomotive units are connected together with the sanding systems controlled from a single location.

In the present invention the fiow of air to trap is controlled by the combined operation of a solenoid operated on-ofr valve 28 and a sensor-charger valve 30 connected to nozzle 18 of trap 10 as shown in FIG. 1. Solenoid valve 28 may be of any conventional design such as that shown in detail in FIG. 3. Its function is to open and close the air flow entrance to nozzle 18 in response to an electrical signal carried to the coil 32 of the valve by conductors 34. Energization of coil 32 will draw armature valve member 36 into the coil against the bias of spring 38 thereby opening center orifice 40 in diaphragm member 42. The opening of orifice 40 will cause the pressure in chamber 44 to drop allowing the higher pressure in chamber 46 to lift diaphragm member 42 from seat 48 and thereby permit air to flow from inlet 50 into the trap 10 through nozzle 18. When coil 32 is deenergized armature valve member 36 will close orifice 40 causing the resulting pressure build-up in chamber 44 through bleed orifices 52 in the diaphragm to seat diaphragm member 42 against seat 48 to thereby shut off flow to nozzle 18.

The desired initial high volume of air blast for cleaning the trap followed by a reduced flow for normal sanding is provided by the action of sensor-charger valve 30. The construction of valve 30 is shown in detail in FIG. 2 and includes a two-piece body comprised of a first body member 54 having an inlet port 56 threaded into one end of a second body member 58 having an outlet port 60. As shown in FIG. 1, the outlet port 60 of valve 30 is connected to solenoid valve 28 by a conduit 62 and air under pressure is carried from the main reservoir of the locomotive (not shown) to valve 30 by a conduit 64 connected to inlet port 56.

Clamped between body members 54 and 58 is a piston sleeve 66 having a differential piston member 68 slidably mounted therein. Piston 68 is comprised of a head portion 70 slidably engaged with the inside of body member 58 and a stern portion 72 slidably engaged with the inside of sleeve 66. Head 70 and stem 72 are sealed to their respective sliding surfaces by O-ring members 74 and 76, respectively. The piston 68 is biased outwardly from sleeve 66 by a spring 78. Piston 68 is provided with a center bore 80 which extends out through an orifice plug 82 mounted in head 70. Radial ports 84 are provided in stem .72 to communicate bore 80 with the outside of the stem.

A poppet valve 86 is mounted in the inlet end of sleeve 66 as shown. The poppet valve is comprised of a valve -member 88 biased to closed position against a seat 90 by a spring 92. A sanding orifice 94 is provided in the wall of sleeve 66 as shown.

The sensor-charger valve operates as follows. With the entrance to sanding nozzle 18 shut off (solenoid coil 32 deenergized) the sensor-charger valve 30 and line 62 will be pressurized to full main reservoir pressure. During this condition piston 68 will be forced to the right against the bias of spring 78 due to the difference in the pressure responsive areas of head 70 and stem 72. With piston 68 forced to the right, the end of stem 72 will force poppet valve member 88 to the right against the bias of spring 92 to thus hold the poppet valve in open position.

The parts will remain in the above described position as long as sensor-charger valve 30 remains fully pressurized.

To initiate sanding, solenoid valve 28 is opened by energizing coil 32. If there are no restrictions in the sand delivery line 12, the solenoid valve 28 passes compressed air into the trap 10 faster than can be supplied by both poppet valve 86 and sanding orifice 94. A decrease in pressure results at the outlet of valve 30 allowing return spring 78 to move piston 70 to the left which, in turn,

allows spring 92 to close poppet valve 86. With piston 68 moved to the left allowing the poppet valve 86 to close all air passing through the sensor-charger valve must pass through the restricted sanding orifice 94 which is designed to meter the desired volume of air for normal sanding at trap 10.

From the foregoing it will be appreciated that upon the initial opening of solenoid valve 28 (with poppet valve 86 held open) there will be an initial high volume blast of air delivered to trap 10 which serves to clean out nozzle 18 and sand delivery line 12.

When sanding is turned off by deenergizing the solenoid valve coil 32, the solenoid valve will close causing sensorcharger valve to again be fully pressurized. With valve 30 fully pressurized, piston 68 will again be forced to the right causing the poppet valve 86 to open.

As stated previously, during normal sanding with the solenoid valve open the pressure on piston head 70 is insufficient to overcome the bias of spring 78. If, however, an obstruction should develop in the sand trap delivery line 12, for example, the resultant pressure build-up at outlet port 60 will force piston 68 to the right and thereby open poppet valve 86. The opening of poppet valve 86 will admit a large volume of high pressure air to the sand trap to thereby clear the obstruction in the sand delivery line. When the obstruction is cleared the pressure at outlet port 60 will again drop allowing spring 78 to move piston 68 back to the left causing the poppet valve to close. It will be noted that upon such increased flow in response to the occurrence of an obstruction there will be a tendency for the pressure build-up in trap 10 to be limited by air leakage up through the sand in sand supply line 14 and sand box 16 out to atmosphere. To prevent such leakage flow and thereby fully utilize the increased air flow delivered by valve 30 for removing obstructions in sand delivery line 12, a check valve 26 is provided in sand supply line 14 which operates to allow free passage of sand from box 16 to trap 10 but will close automatically to prevent air flow from the trap up line 14 and out through the sand in box 16. Check valve 26 may be of any suitable construction capable of performing the intended function. A check valve specifically designed for use in the sanding mechanism of this invention is shown in FIGS. 10 and 11.

The purpose of orifice plug 82 mounted in head 70 of piston 68 is to adjust the volume of air flow through bore and thereby adjust the pressure sensing characteristics of piston 68.

Referring now to the modification shown in FIGS. 4-6, this simplified system includes a sand trap 96 and a solenoid valve 98 which may be of identical construction to the sand trap and solenoid valve of the preferred embodiment described above. Air from the main reservoir (not shown) is carried to an orifice T assembly or air restriction means 100 by a line 112 from which it flows to a pair of sand trap (only one shown) through lines 102 and 104. T assembly 100 is of two-piece construction comprising a pipe bracket section 106 and an orifice mounting section 108 fastened together by machine screws 110. Line 112 from the main reservoir is connected to inlet port 114 and lines 102 and 104 leading to the two sand traps are connected to outlet port 116 and 118 of the orifice T. Air from inlet port 114 fiows through restricted sanding orifices 120 and 122 mounted in section 108 as shown in FIG. 5. Orifice plugs 120 and 122 may be readily removed for cleaning or replacement from outside the orifice T assembly without disturbing the pipe connections to the pipe bracket section by simply remov ing access plugs 124 and 126.

The above described system operates as follows. With the entrance to sanding nozzle of trap 96 shut off (solenoid coil deenergized), T 100 and lines 102 and 104 will be pressurized to full main reservoir pressure. When sanding at trap 96 is initiated by opening the solenoid valve 98, air under pressure will flow from inlet line 112 through orifice T 100 and into the sand trap through line 102. Upon initial opening of the solenoid valve the air in line 102 will immediately be dumped into trap 96, such line 102 acting as an accumulator chamber. This initial high volume blast of air serves to clear any obstructions in the sand delivery line of trap 96 (not shown). After this initial high volume blast of air terminates a reduced flow of air metered by orifice 120 will continue to be supplied to the sand trap for normal sanding.

Referring to the preferred embodiment shown in FIGS. 7-13, the sanding system includes a sand trap 128 having a sand outlet 130 for connection to a sand delivery line (not shown). Trap 128 is provided with a sand on-off valve 132 and a sand pipe check valve 134 through which sand from a sand box (not shown) is fed by gravity to the trap. Trap 128 has a nozzle 136 (FIG. 9) through which air under pressure is introduced to carry sand from the trap out through sand outlet 130 to the rails.

Just as in the FIGS. l-3 embodiment described above, the flow of air to trap 128 is controlled by the combined operation of a solenoid operated on-oif valve 138 and a sensor-charger valve 140 removably mounted on mounting bracket 142 which, in turn, is removably mounted on trap 128 by captive bolts 144 (FIG. 8). Solenoid valve 138 may be of any conventional design such as that shown in FIGS. 3 and 9. Since solenoid valve 138 used in this embodiment (FIG. 9) is identical to that shown and described in the FIGS. l-3 embodiment, a detailed description of valve 138 will not be repeated at this point. The function of valve 138 is to provide on-off control of air flow from inlet chamber 146 to outlet chamber 148 in bracket 142.

The desired initial high volume of air blast for cleaning the trap followed by a reduced flow for normal sanding is provided by the action of sensor-charger valve 140. The construction of valve 140 is shown in FIG. 9 and is similar to that shown in FIG. 2 described previously. As will be explained, there are some differences which provide certain important advantages.

Valve 140 includes a body member 150 threaded into a boss 152 on bracket 142 which opens into chamber 146 in the bracket. Body 150 is provided with an air inlet port 154 adapted for connection to a source of air under pressure. 'Slidably mounted in the end of body 150 is a differential piston member 156 comprised of a head portion 158 slidably engaged with the inside of boss 152 and a stem portion 160 slidably engaged with the inside of body 150. Head 158 and stem 160 are sealed to their respective sliding surfaces by O-ring members 162 and 164, respectively. The piston156 is biased outwardly from body 150 by a spring 166. Its outward travel is limited by a shoulder 168 formed at the inner end of boss 152. Piston 156'is provided with a center bore 170 which funnels outwardly as at 172. Ports 174 are provided in stem 160 to communicate bore 170 with the inlet side of valve 140.

A poppet valve 176 is mounted at the inlet end of body 150 and is comprised of a valve member 178 biased to closed position against an insert seat 180 by a spring 182. As clearly shown in FIG. 13, a groove 184 is provided in poppet valve member 178 which serves as a sanding orificeas will be explained.

' Sensor-charger valve 140 operates as follows. With the chamber 148 leading tonozzle 136 shut off (solenoid valve 138 closed), the sensor-charger valve 140 will be pressurized to full main reservoir pressure. During this condition piston 156 will be forced to the right against the bias of springy166 due to the difference in. the pressure responsive areas on head 158 and stem 160. With piston 156 forced to ,the right, the end of stem 160 will force poppet valve member 178 to the right against the bias of spring 182 thus hold the poppet valve in open position. It will remain in the above-described position as long as sensor-charger valve 140remains fully pressurized. To initiate sanding, solenoid valve 138 is opened. If

there are no restrictions in the sand delivery line the solenoid valve 138 passes compressed air from chamber 146 to chamber 148 in bracket 142 and then into the trap through nozzle 136. Such initial flow is faster than can be supplied by poppet valve 176 and thus a decrease in pressure results at the outlet of valve allowing return spring 166 to move piston 156 to the left which, in turn, allows spring 182 to close poppet valve 176. With piston 156 moved to the left allowing the poppet valve 176 to close, all air passing through the sensor-charger valve must pass through the restricted sanding orifice 184 which is designed to meter the desired volume of air for normal sanding at trap 128.

From the foregoing it will be appreciated that upon the initial opening of the solenoid valve (with poppet valve 176 held open) there will be an initial high volume of air delivered to trap 128 which serves to clean out nozzle 136 and the sand delivery line. It should also be noted at this point that when the poppet valve 176 moves to its open position the sanding orifice groove 184 will be left exposed allowing the increased volume of air flow to produce a cleaning action to the sanding orifice groove. Thus it is seen that each time the poppet valve member 178 moves to the charging position, the sanding orifice slot 184 therein will be subjected to a cleaning operation.

When sanding is turned off by closing the solenoid valve 138 sensor-charger valve 140 will again become fully pressurized. With valve 140 fully pressurized, a piston 156 will again be forced to the right causing the poppet valve 176 to open.

As stated previously, during normal sanding with the solenoid valve open the pressure on piston head 158 is insufficient to overcome the bias of spring 166. If, however, an obstruction should develop in the sand trap or the delivery line, for example, the resultant pressure built up at the outlet to the sensor-charger valve will force piston 156 to the right and thereby open poppet valve 176. Opening of poppet valve 176 will admit a large volume of high pressure air to the sand trap to thereby clear the obstruction in the sand delivery line. When the obstruction is cleared the pressure at the outlet of the sensorcharger valve will again drop allowing spring 166 to move piston 156 back to the left causing the poppet valve 176 to close.

It will be noted that upon such increased flow in response to the occurrence of an obstruction there will be a tendency for the pressure build-up in trap 128 to be limited by air leakage up through the sand in the sand supply conduit and out through the sand box to atmosphere. To prevent such leakage flow and thereby fully utilize the increased air flow delivered by valve 140 for removing obstructions in the sand delivery line, a check valve 134 is provided in the sand supply conduit which operates to allow free passage of sand from the sand box to the trap but will close automatically to prevent air flow from the trap up through the sand delivery conduit and out through the sand box. As stated previously, with respect to the FIGS. l-3 embodiment, the check valve employed for this purpose may be of any suitable construc tion capable of performing the intended function. The check valve shown in FIGS. 10 and 11 is specifically designed for use in the sanding mechanism of this invention. Since the detailed construction and operation of such check valve is not per se a part of this invention a detailed description will not be made here. Broadly speaking, however, check valve 134 is comprised of a ball member 186 adapted for cooperation with a resilient seat member 188 to allow sand flow into trap 128 during normal sanding conditions and to close off the sand inlet passage upon a pressure build-up in the trap.

Although two embodiments of the present invention have been illustrated and described, it will be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the 7 spirit of the invention or from the scope of the appended claims.

I claim:

1. A sanding system comprising a sander, a discharge pipe leading from such sander, means for alternately applying high pressure clean-out and low pressure sanding air to said discharge pipe, means for sensing a clogging condition in said pipe, and means responsive to said sensing means for applying clean-out air to said pipe to remove said condition.

2. A sanding system comprising a sander having a sand supply line connected thereto, a discharge pipe leading from said sander, means for alternately applying high pressure clean-out and low pressure sanding air to said discharge pipe, means for sensing a clogging condition in said pipe, means responsive to said sensing means for applying clean-out air to said pipe to remove said condition, and a check valve means mounted in the sand supply line to prevent air flow leakage out through the sand supply line when the air pressure in the sander is increased to remove said clogging condition.

3. A sanding system comprising a sander, a discharge pipe leading from said sander, means for alternately applying high pressure clean-out and low pressure sanding air to said discharge pipe, means for sensing a clogging condition in said pipe, and means responsive to said sensing means for applying clean-out air to said pipe to remove said clogging condition, said means for alternately applying high pressure clean-out and low pressure sanding air including a source of air under pressure connected to said sander by an air delivery conduit means, an ON- OFF valve means in said air delivery conduit means, and an air restriction means in said delivery conduit means located upstream from said ON-OFF valve means, said air delivery conduit between said ON-OFF valve means and said air restriction means acting as an accumulator chamber to admit a high volume blast of air to said sand trap for cleaning upon initial opening of said ON-OFF valve means followed by a reduced volume of air for normal sanding metered by said air restriction means.

4. A sanding mechanism comprising:

a sand trap;

a source of air under pressure connected to said sand trap by an air delivery conduit means;

an on-off valve means in said air delivery conduit means;

and

a sensor-charger valve means in said delivery conduit means located upstream from said on-off valve means, said sensor-charger valve means having an inlet and an outlet and adapted to admit an initial large volume air blast to said trap upon opening of said on-otf valve means and to thereafter permit a reduced vol ume of air to flow to said sand trap as long as said on-oif valve means remains open, said sensor-charger valve means being further adapted to admit an increased volume of air to said trap in response to an increase of pressure at the outlet of said sensorcharger valve means as might result from the occurrence of an air flow obstruction in the sand trap sand delivery line.

5. A sanding mechanism according to claim 4 in which said sensor-charger valve means includes a poppet valve means and a pressure sensitive piston means operative to open said poppet valve means to increase air flow through said sensor-charger valve means upon a pressure build-up at the outlet of said sensor-charger valve means.

6. A sanding mechanism according to claim 5 in which said pressure sensitive piston means includes a diiferential piston member having a head and a stem with said head facing the outlet of said sensor-charger valve means.

7. A sanding mechanism according to claim 6 in which said pressure sensitive piston means further includes a return spring operable to move said differential piston member in a direction permitting said poppet valve means to open.

8. A sanding mechanism according to claim 7 in which said sensor-charger valve means further includes a sleeve member with said pressure sensitive piston means mounted in one end thereof and with said poppet valve means mounted in the other end thereof.

9. A sanding mechanism according to claim 8 in which said sleeve member has a sanding orifice in the wall thereof.

10. A sanding mechanism according to claim 1 in which said air delivery conduit means includes a bracket member removably mounted on said sand trap, said on-otf valve means and said sensor-charger valve means mounted on said bracket member, said bracket member having internal chambers adapted to pass air from said sensorcharger valve to said on-off valve and then to said trap.

11. A sanding mechanism according to claim 4 in which said sensor-charger valve means includes a poppet valve means and a pressure sensitive piston means operative to open 'said poppet valve means to increase air fiow through said sensor-charger valve means upon a pressure build-up at the outlet of said sensor-charger valve means, said poppet valve means including a poppet valve member having a sanding orifice therethrough.

12. A sanding mechanism according to claim 11 in which said sanding orifice is in the form of a groove in the outer periphery of said poppet valve member.

13. A sanding mechanism including a sand trap connected to a source of air under pressure by an air delivery conduit comprising:

a solenoid operated on-otf valve means in said delivery conduit; and

a sensor-charger valve means in the delivery conduit located upstream from said on-olf valve means, said sensor-charger valve means having an inlet and an outlet and adapted to admit an initial large volume air blast to the sand trap upon initial opening of said on-oif valve means and to thereafter permit a reduced volume of air to flow to the sand trap as long as said on-off valve means remains open, said sensorcharger valve means being further adapted to admit an increased volume of air to the sand trap in response to an increase of pressure at the outlet of said sensor-charger valve means as might result from the occurrence of anair flow obstruction in the sand trap sand delivery line.

14. In a sanding mechanism having a sand trap connected to a source of air pressure by an air delivery line and connected to a source of sand by a sand supply line;

a solenoid operated on-otf valve means to said delivery conduit;

a sensor-charger valve means in the delivery conduit located upstream from said on-otf valve means, said sensor-charger valve means having an inlet and an outlet and adapted to admit an initial large volume air blast to the sand trap upon opening of said on-off valve means and to thereafter permit a reduced volume of air to flow to the sand trap as long as said on-ofl valve means remains open, said sensor-charger valve means being further adapted to admit an increased volume of air to the sand trap in response to an increase of pressure at the outlet of said sensorcharger valve means as might result from the occurrence of an air flow obstruction in the sand trap sand delivery line; and

a check valve means mounted in the sand supply line to prevent air flow leakage out through the sand sup ply line when the air pressure in the sand trap is increased by the operation of said sensor-charger valve.

15. A sanding mechanism comprising:

a sand trap;

a source of air under pressure connected to the sand trap by an air delivery conduit means;

an on-off valve means in said air delivery conduit means; and

air restriction means in said delivery conduit means located upstream from said on-ofi valve means, said air delivery conduit between said on-olf valve means and said air restriction means acting as an accumulator chamber to admit a high volume blast of air to said sand trap for cleaning upon initial opening of said on-otf valve means followed by a reduced volume of air for normal sanding metered by said air restriction means.

16. A sanding mechanism according to claim 15 in which said restriction means is comprised of an orifice T having a removable sanding orifice plug mounted therein through which air must pass from said source to said trap.

17. A sanding mechanism comprising:

a sand trap having a sand supply line connected thereto;

a source of air under pressure connected to the sand trap by an air delivery conduit means;

an ON-OFF valve means in said air delivery conduit means;

air restriction means in said delivery conduit means located upstream from said on-ofl? valve means, said air delivery conduit between said on-otf valve means and said air restricting means acting as an accumulator chamber to admit a high volume blast of air to said sand trap for cleaning upon initial opening of said on-01f valve means followed by a reduced volume of air for normal sanding metered by said air restriction means; and

a check valve means mounted in said sand supply line to prevent air flow leakage out through said sand supply line when the air pressure in said sand trap is increased by said high volume blast of clean-out 2.11.

18. A sanding control apparatus for mounting on a sand trap comprising:

a solenoid operated on-ofi? valve means fluidly connected to the sand trap and adapted to permit and shut oif flow to the trap;

a sensor-charger valve means fluidly connected to said solenoid operated on-oflf valve means and located upstream from said on-off valve means, said sensorcharger valve means having an inlet and an outlet and adapted to admit an initial large volume air blast to the sand trap upon the initial opening of said on-ofi valve means and to thereafter permit a reduced volume of air to flow to the sand trap as long as said onoff valve remains open, said sensor charger valve means being further adapted to admit an increased volume of air to the sand trap in response to an increase of pressure at the outlet of said sensor-charger valve means as might result from the occurrence of an air flow obstruction in the sand trap sand delivery line; and

a bracket member removably mounted on the sand trap, said on-ofi valve means and said sensor-charger valve means mounted on said bracket member, said bracket member having internal chambers adapted to pass air from said sensor-charger valve to said on-off valve and then to the trap.

References Cited UNITED STATES PATENTS 3,075,318 1/1963 Dillard et a1. 51-8 3,084,484 4/1963 Hall et a1. 51-8 3,049,141 8/1962 Beetty et a1. 137-494 3,103,950 9/1963 Gulick 137-494 2,291,874 8/1942 Campbell 291-3 2,324,274 7/1943 Baldwin 291-3 2,386,006 10/1945 Salford 291-3 ARTHUR L. LA POINT, Primary Examiner.

J. S. OVERLROLSER, Examiner.

L. J. SHECHTER, B. FAUST, H. BELTRAN,

Assistant Examiners.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,359,024 December 19, 1967 James I Morgan error appears in the above numbered pat- It is hereby certified that t the said Letters Patent should read as ent requiring correction and tha corrected below.

Column 8, line 9, for the claim reference numeral "1" read 4 Signed and sealed this 14th day of January 1969.

(SEAL) Attest:

EDWARD J. BRENNER Edward M. Fletcher, Jr.

Commissioner of Patents Attesting Officer 

1. A SANDING SYSTEM COMPRISING A SANDER, A DISCHARGE PIPE LEADING FROM SUCH SANDER, MEANS FOR ALTERNATELY APPLYING HIGH PRESSURE CLEAN-OUT AND LOW PRESSURE SANDING AIR TO SAID DISCHARGE PIPE, MEANS FOR SENSING A CLOGGING CONDITION IN SAID PIPE, AND MEANS RESPONSIVE TO SAID SENSING MEANS FOR APPLYING CLEAN-OUT AIR TO SAID PIPE TO REMOVE SAID CONDITION. 